How to stop toxic blooms clogging up Lake Erie

THIS is not a health drink. The waters of North America's Lake Erie turned lurid green this week, thanks to a bloom of toxic bacteria. The bloom has now receded and the water is drinkable again, but the challenge is to stop it happening again.

The blue-green cyanobacteria Microcystis aeruginosa built up at the western end of the lake, which is the main source of drinking water for Toledo, Ohio. The bacterium produces a toxin called microcystin, forcing Toledo to turn off the water supply.

Such blooms are increasingly common in Lake Erie, as phosphorus from fertilisers runs into the water and feeds the cyanobacteria.

To prevent blooms, Ohio must stem the flow of phosphorus, says Jeffrey Reutter of Ohio State University in Columbus. Farmers should test soil to help them only use as much fertiliser as is necessary, and apply it when planting so unused phosphorus isn't left lying around.

This article appeared in print under the headline "Don't feed the microbes"

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